Material feeding systems are well known which employ parallel links pivotally connected to a horizontal support member at the top and a base at the bottom to form a parallelogram arrangement which can be rocked by some hydraulic arrangement or electromechanical means. Such an arrangement for an automatic material feeding apparatus is shown in U.S. Pat. No. 3,952,883 issued to Phillips. A specialized parallelogram arrangement with an arm extending from the horizontal top edge of the parallelogram is shown in U.S. Pat. No. 1,757,772 issued to Johnson, and a stacking and palletizing system is shown using such an apparatus in U.S. Pat. No. 3,392,852 issued to Tegner.
The parallelogram linkage systems for material feeding and stacking are primarily adapted for fully automated operations and have the hydraulic or electomechanical apparatus to control the swing of the linkage parallelogram so that the linkage does not fully collapse. Such systems are not well adapted for semi-automated use or use where only human force is available.